Catalyst compositions comprising the porous crystalline MCM-56 material manufactured by this method may be used to effect various chemical conversions, and are especially valuable for use in a process for producing alkylaromatics, particularly ethylbenzene and cumene, or for use in a process for oligomerization of olefins, particularly for production of dimers, trimers and tetramers of olefins, e.g., ethylene, propylene, butylene, or mixtures thereof.
Ethylbenzene and cumene are valuable commodity chemicals that are used industrially for the production of styrene monomer and coproduction of phenol and acetone respectively. Ethylbenzene may be produced by a number of different chemical processes but one process that has achieved a significant degree of commercial success is the vapor phase alkylation of benzene with ethylene in the presence of a solid, acidic ZSM-5 zeolite catalyst. Examples of such ethylbenzene production processes are described in U.S. Pat. No. 3,751,504 (Keown), U.S. Pat. No. 4,547,605 (Kresge), and U.S. Pat. No. 4,016,218 (Haag).
More recently focus has been directed at liquid phase processes for producing ethylbenzene from benzene and ethylene since liquid phase processes operate at a lower temperature than their vapor phase counterparts and hence tend to result in lower yields of by-products. For example, U.S. Pat. No. 4,891,458 (Innes) describes the liquid phase synthesis of ethylbenzene with zeolite beta, whereas U.S. Pat. No. 5,334,795 (Chu) describes the use of MCM-22 in the liquid phase synthesis of ethylbenzene.
Cumene has for many years been produced commercially by the liquid phase alkylation of benzene with propylene over a Friedel-Craft catalyst, particularly solid phosphoric acid or aluminum chloride. More recently, however, zeolite-based catalyst systems have been found to be more active and selective for propylation of benzene to cumene. For example, U.S. Pat. No. 4,992,606 (Kushnerick) describes the use of MCM-22 in the liquid phase alkylation of benzene with propylene.
Alkylation processes for producing ethylbenzene and cumene in the presence of currently used catalysts inherently produce polyalkylated species as well as the desired monoalkylated product. The polyalkylated species are typically transalkylated with benzene to produce additional monoalkylated product, for example ethylbenzene or cumene, either by recycling the polyalkylated species to the alkylation reactor or, more frequently, by feeding the polyalkylated species to a separate transalkylation reactor having a transalkylation catalyst. Examples of catalysts which have been used in the alkylation of aromatic species, such as alkylation of benzene with ethylene or propylene, and in the transalkylation of polyalkylated species, such as polyethylbenzenes and polyisopropylbenzenes, are listed in U.S. Pat. No. 5,557,024 (Cheng) and include MCM-49, MCM-22, PSH-3, SSZ-25, zeolite X, zeolite Y, zeolite Beta, acid dealuminized mordenite and TEA-mordenite. Transalkylation over a small crystal (<0.5 micron) form of TEA-mordenite is also disclosed in U.S. Pat. No. 6,984,764.
MCM-56 is a layered oxide material, rather than a three dimensionally ordered zeolite, in which each layer in MCM-56 is porous and has a framework structure closely related to that of MCM-22 and other MCM-22 family materials.
The term “MCM-22 family material” (or “material of the MCM-22 family” or “molecular sieve of the MCM-22 family”), as used herein, includes one or more of:    (i) molecular sieves made from a common first degree crystalline building block unit cell, which unit cell has the MWW framework topology. (A unit cell is a spatial arrangement of atoms which if tiled in three-dimensional space describes the crystal structure. Such crystal structures are discussed in the “Atlas of Zeolite Framework Types”, Fifth edition, 2001, the entire content of which is incorporated as reference);    (ii) molecular sieves made from a common second degree building block, being a 2-dimensional tiling of such MWW framework topology unit cells, forming a monolayer of one unit cell thickness, preferably one c-unit cell thickness;    (iii) molecular sieves made from common second degree building blocks, being layers of one or more than one unit cell thickness, wherein the layer of more than one unit cell thickness is made from stacking, packing, or binding at least two monolayers of one unit cell thickness. The stacking of such second degree building blocks can be in a regular fashion, an irregular fashion, a random fashion, or any combination thereof; and    (iv) molecular sieves made by any regular or random 2-dimensional or 3-dimensional combination of unit cells having the MWW framework topology.
The MCM-22 family materials are characterized by having an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 3.57±0.07 and 3.42±0.07 Angstroms (either calcined or as-synthesized). The MCM-22 family materials may also be characterized by having an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstroms (either calcined or as-synthesized). The X-ray diffraction data used to characterize said molecular sieve are obtained by standard techniques using the K-alpha doublet of copper as the incident radiation and a diffractometer equipped with a scintillation counter and associated computer as the collection system. Materials that belong to the MCM-22 family include MCM-22 (described in U.S. Pat. No. 4,954,325); PSH-3 (described in U.S. Pat. No. 4,439,409); SSZ-25 (described in U.S. Pat. No. 4,826,667); ERB-1 (described in European Patent No. 0293032); ITQ-1 (described in U.S. Pat. No. 6,077,498); ITQ-2 (described in International Patent Publication No. WO97/17290); ITQ-30 (described in International Patent Publication No. WO2005118476); MCM-36 (described in U.S. Pat. No. 5,250,277); MCM-49 (described in U.S. Pat. No. 5,236,575); MCM-56 (described in U.S. Pat. No. 5,362,697); UZM-8 (described in U.S. Pat. No. 6,756,030); and UZM-8HS (described in U.S. Pat. No. 7,713,513). The entire contents of said patents are incorporated herein by reference.
It is to be appreciated the MCM-22 family molecular sieves described above are distinguished from conventional large pore zeolite alkylation catalysts, such as mordenite, in that the MCM-22 materials have 12-ring surface pockets which do not communicate with the 10-ring internal pore system of the molecular sieve.
The zeolitic materials designated by the IZA-SC as being of the MWW topology are multi-layered materials which have two pore systems arising from the presence of both 10 and 12 membered rings. The Atlas of Zeolite Framework Types classes five differently named materials as having this same topology: MCM-22, ERB-1, ITQ-1, ITQ-2, PSH-3, and SSZ-25.
The MCM-22 family molecular sieves have been found to be useful in a variety of hydrocarbon conversion processes. Examples of MCM-22 family molecular sieve are MCM-22, MCM-49, MCM-56, ITQ-1, ITQ-2, PSH-3, SSZ-25, ERB-1, UZM-8, and UZM-8HS.
MCM-56 and its synthesis are described in U.S. Pat. No. 5,362,697 (Fung) and U.S. Pat. No. 5,827,491 (Emerson). U.S. Pat. No. 5,453,554 (Cheng) discloses the use of MCM-56 as a catalyst in the alkylation of aromatic compounds with short chain (1 to 5 carbon atoms) alkylating agents. As disclosed in FIGS. 6 and 7 of U.S. Pat. No. 5,453,554, MCM-56 offers potential advantages over MCM-22 for the production of ethylbenzene and cumene, particularly under liquid phase conditions, since MCM-56 is a more active alkylation catalyst than its zeolitic counterpart MCM-22. The entire disclosures of U.S. Pat. Nos. 5,362,697, 5,827,491 and 5,453,554 are incorporated herein by reference.
When synthesizing MCM-56 by currently available means, impurity formation is a problem. Such preparation of MCM-56 presents a unique challenge, especially on a large scale, because it is an intermediate. The MCM-56 product produced may be transient and undergo further change during the manufacturing process. In particular, the initially exfoliated, randomly packed MCM-56 sheets (with MCM-22 topology and one 25 Å thick unit cell) become gradually organized into a 3-dimensional framework ordered in the c-direction, which is formally the zeolite MCM-49. This problem with the transient nature of MCM-56 is compounded by the difficulty in determining its complete formation and exhaustion of the amorphous synthesis gel.
According to the present invention, it has now unexpectedly been found that we can significantly avoid the above problems with a beneficial extension of the MCM-56 synthesis window. This improved method provides MCM-56 crystal product unencumbered by impurities, e.g., crystals of ferrierite, kenyaite, or MCM-22 family materials, such as MCM-49 materials, as identified by X-ray diffraction. This requires critical adjustment of the composition of the crystallization reaction mixture and control of the crystallization conditions, as detailed herein.